Among apparatuses for obtaining information about the surface of a measuring object such as surface roughness and profile, one is known that employs a contact probe, see Mitutoyo Co., Ltd, Products Information (found online on Dec. 19, 2006) at Internet URL: http://www.mitutoyo.co.jp/eng/products/keijyou_hyomen/hyomen—01.html. In this surface nature measuring apparatus, the contact probe makes contact with and moves relative to the surface of a measuring object. The distance the contact probe moves along the surface profile of the measuring object is detected to measure the profile of the measuring object. However, the contact probe has a limitation in measuring the surface profile. For example, the inner profile of a pore can be measured using a small contact probe when the pore has a relatively large cross-sectional area with a nearly constant inner diameter in the depth direction. However, when the pore has an inner diameter that is small at the entrance and increases in the depth direction, a small probe that can pass through the entrance of a pore does not make contact with the inner wall at the bottom. In such a case, measurement is inconveniently difficult.